Upgrade to `nim-json-rpc` v0.4.2 and chronos v4 (#64)

* Add json de/serialization lib from codex to handle conversions

json-rpc now requires nim-json-serialization to convert types to/from json. Use the nim-json-serialization signatures to call the json serialization lib from nim-codex (should be moved to its own lib)

* Add ethers implementation for setMethodHandler

Was removed in json-rpc

* More json conversion updates

* Fix json_rpc.call returning JsonString instead of JsonNode

* Update exceptions

Use {.async: (raises: [...].} where needed
Annotate provider with {.push raises:[].}
Format signatures

* Start fixing tests (mainly conversion fixes)

* rename sender to `from`, update json error logging, add more conversions

* Refactor exceptions for providers and signers, fix more tests

- signer procs raise SignerError, provider procs raise ProviderError
- WalletError now inherits from SignerError
- move wallet module under signers
- create jsonrpo moudle under signers
- bump nim-json-rpc for null-handling fixes
- All jsonrpc provider tests passing, still need to fix others

* remove raises from async annotation for dynamic dispatch

- removes async: raises from getAddress and signTransaction because derived JsonRpcSigner methods were not being used when dynamically dispatched. Once `raises` was removed from the async annotation, the dynamic dispatch worked again. This is only the case for getAddress and signTransaction.
- add gcsafe annotation to wallet.provider so that it matches the base method

* Catch EstimateGasError before ProviderError

EstimateGasError is now a ProviderError (it is a SignerError, and SignerError is a ProviderError), so EstimateGasErrors were not being caught

* clean up - all tests passing

* support nim 2.0

* lock in chronos version

* Add serde options to the json util, along with tests

next step is to:
1. change back any ethers var names that were changed for serialization purposes, eg `from` and `type`
2. move the json util to its own lib

* bump json-rpc to 0.4.0 and fix test

* fix: specify raises for getAddress and sendTransaction

Fixes issue where getAddress and sendTransaction could not be found for MockSigner in tests. The problem was that the async: raises update had not been applied to the MockSigner.

* handle exceptions during jsonrpc init

There are too many exceptions to catch individually, including chronos raising CatchableError exceptions in await expansion. There are also many other errors captured inside of the new proc with CatchableError. Instead of making it more complicated and harder to read, I think sticking with excepting CatchableError inside of convertError is a sensible solution

* cleanup

* deserialize key defaults to serialize key

* Add more tests for OptIn/OptOut/Strict modes, fix logic

* use nim-serde instead of json util

Allows aliasing of de/serialized fields, so revert changes of sender to `from` and transactionType to `type`

* Move hash* shim to its own module

* address PR feedback

- add comments to hashes shim
- remove .catch from callback condition
- derive SignerError from EthersError instead of ProviderError. This allows Providers and Signers to be separate, as Ledger does it, to isolate functionality. Some signer functions now raise both ProviderError and SignerError
- Update reverts to check for SignerError
- Update ERC-20 method comment

* rename subscriptions.init > subscriptions.start

ethers.nimble

@@ -5,10 +5,11 @@ license = "MIT"
 
 requires "nim >= 1.6.0"
 requires "chronicles >= 0.10.3 & < 0.11.0"
-requires "chronos >= 3.0.0 & < 4.0.0"
+requires "chronos >= 4.0.0 & < 4.1.0"
 requires "contractabi >= 0.6.0 & < 0.7.0"
 requires "questionable >= 0.10.2 & < 0.11.0"
-requires "json_rpc"
+requires "json_rpc >= 0.4.0 & < 0.5.0"
+requires "serde >= 0.1.1 & < 0.2.0"
 requires "stint"
 requires "stew"
 requires "eth"

ethers/erc20.nim

@@ -76,5 +76,5 @@ method transferFrom*(token: Erc20Token,
                      spender: Address,
                      recipient: Address,
                      amount: UInt256): ?TransactionResponse {.base, contract.}
-  ## Moves `amount` tokens from `from` to `to` using the allowance
+  ## Moves `amount` tokens from `spender` to `recipient` using the allowance
   ## mechanism. `amount` is then deducted from the caller's allowance.

ethers/nimshims/hashes.nim

@@ -0,0 +1,49 @@
+## Fixes an underlying Exception caused by missing forward declarations for
+## `std/json.JsonNode.hash`, eg when using `JsonNode` as a `Table` key. Adds
+## {.raises: [].} for proper exception tracking. Copied from the std/json module
+
+import std/json
+import std/hashes
+
+{.push raises:[].}
+
+when (NimMajor) >= 2:
+  proc hash*[A](x: openArray[A]): Hash =
+    ## Efficient hashing of arrays and sequences.
+    ## There must be a `hash` proc defined for the element type `A`.
+    when A is byte:
+      result = murmurHash(x)
+    elif A is char:
+      when nimvm:
+        result = hashVmImplChar(x, 0, x.high)
+      else:
+        result = murmurHash(toOpenArrayByte(x, 0, x.high))
+    else:
+      for a in x:
+        result = result !& hash(a)
+      result = !$result
+
+func hash*(n: OrderedTable[string, JsonNode]): Hash
+
+func hash*(n: JsonNode): Hash =
+  ## Compute the hash for a JSON node
+  case n.kind
+  of JArray:
+    result = hash(n.elems)
+  of JObject:
+    result = hash(n.fields)
+  of JInt:
+    result = hash(n.num)
+  of JFloat:
+    result = hash(n.fnum)
+  of JBool:
+    result = hash(n.bval.int)
+  of JString:
+    result = hash(n.str)
+  of JNull:
+    result = Hash(0)
+
+func hash*(n: OrderedTable[string, JsonNode]): Hash =
+  for key, val in n:
+    result = result xor (hash(key) !& hash(val))
+  result = !$result

ethers/provider.nim

@@ -1,4 +1,5 @@
 import pkg/chronicles
+import pkg/serde
 import pkg/stew/byteutils
 import ./basics
 import ./transaction
@@ -14,15 +15,15 @@ type
   Provider* = ref object of RootObj
   ProviderError* = object of EthersError
   Subscription* = ref object of RootObj
-  EventFilter* = ref object of RootObj
+  EventFilter* {.serialize.} = ref object of RootObj
     address*: Address
     topics*: seq[Topic]
-  Filter* = ref object of EventFilter
+  Filter* {.serialize.} = ref object of EventFilter
     fromBlock*: BlockTag
     toBlock*: BlockTag
-  FilterByBlockHash* = ref object of EventFilter
+  FilterByBlockHash* {.serialize.} = ref object of EventFilter
     blockHash*: BlockHash
-  Log* = object
+  Log* {.serialize.} = object
     blockNumber*: UInt256
     data*: seq[byte]
     logIndex*: UInt256
@@ -36,9 +37,9 @@ type
     Invalid = 2
   TransactionResponse* = object
     provider*: Provider
-    hash*: TransactionHash
+    hash* {.serialize.}: TransactionHash
-  TransactionReceipt* = object
+  TransactionReceipt* {.serialize.} = object
-    sender*: ?Address
+    sender* {.serialize("from"), deserialize("from").}: ?Address
     to*: ?Address
     contractAddress*: ?Address
     transactionIndex*: UInt256
@@ -51,18 +52,18 @@ type
     cumulativeGasUsed*: UInt256
     effectiveGasPrice*: ?UInt256
     status*: TransactionStatus
-    transactionType*: TransactionType
+    transactionType* {.serialize("type"), deserialize("type").}: TransactionType
   LogHandler* = proc(log: Log) {.gcsafe, raises:[].}
   BlockHandler* = proc(blck: Block) {.gcsafe, raises:[].}
   Topic* = array[32, byte]
-  Block* = object
+  Block* {.serialize.} = object
     number*: ?UInt256
     timestamp*: UInt256
     hash*: ?BlockHash
-  PastTransaction* = object
+  PastTransaction* {.serialize.} = object
     blockHash*: BlockHash
     blockNumber*: UInt256
-    sender*: Address
+    sender* {.serialize("from"), deserialize("from").}: Address
     gas*: UInt256
     gasPrice*: UInt256
     hash*: TransactionHash
@@ -70,7 +71,7 @@ type
     nonce*: UInt256
     to*: Address
     transactionIndex*: UInt256
-    transactionType*: ?TransactionType
+    transactionType* {.serialize("type"), deserialize("type").}: ?TransactionType
     chainId*: ?UInt256
     value*: UInt256
     v*, r*, s*: UInt256
@@ -87,77 +88,104 @@ template raiseProviderError(msg: string) =
 func toTransaction*(past: PastTransaction): Transaction =
   Transaction(
     sender: some past.sender,
-    gasPrice: some past.gasPrice,
-    data: past.input,
-    nonce: some past.nonce,
     to: past.to,
-    transactionType: past.transactionType,
+    data: past.input,
+    value: past.value,
+    nonce: some past.nonce,
+    chainId: past.chainId,
+    gasPrice: some past.gasPrice,
     gasLimit: some past.gas,
-    chainId: past.chainId
+    transactionType: past.transactionType
   )
 
-method getBlockNumber*(provider: Provider): Future[UInt256] {.base, gcsafe.} =
+method getBlockNumber*(
+  provider: Provider): Future[UInt256] {.base, async: (raises:[ProviderError]).} =
+
   doAssert false, "not implemented"
 
-method getBlock*(provider: Provider, tag: BlockTag): Future[?Block] {.base, gcsafe.} =
+method getBlock*(
+  provider: Provider,
+  tag: BlockTag): Future[?Block] {.base, async: (raises:[ProviderError]).} =
+
   doAssert false, "not implemented"
 
-method call*(provider: Provider,
+method call*(
+  provider: Provider,
   tx: Transaction,
-             blockTag = BlockTag.latest): Future[seq[byte]] {.base, gcsafe.} =
+  blockTag = BlockTag.latest): Future[seq[byte]] {.base, async: (raises:[ProviderError]).} =
+
   doAssert false, "not implemented"
 
-method getGasPrice*(provider: Provider): Future[UInt256] {.base, gcsafe.} =
+method getGasPrice*(
+  provider: Provider): Future[UInt256] {.base, async: (raises:[ProviderError]).} =
+
   doAssert false, "not implemented"
 
-method getTransactionCount*(provider: Provider,
+method getTransactionCount*(
+  provider: Provider,
   address: Address,
-                            blockTag = BlockTag.latest):
+  blockTag = BlockTag.latest): Future[UInt256] {.base, async: (raises:[ProviderError]).} =
-                           Future[UInt256] {.base, gcsafe.} =
+
   doAssert false, "not implemented"
 
-method getTransaction*(provider: Provider,
+method getTransaction*(
-                       txHash: TransactionHash):
+  provider: Provider,
-                      Future[?PastTransaction] {.base, gcsafe.} =
+  txHash: TransactionHash): Future[?PastTransaction] {.base, async: (raises:[ProviderError]).} =
+
   doAssert false, "not implemented"
 
-method getTransactionReceipt*(provider: Provider,
+method getTransactionReceipt*(
-                            txHash: TransactionHash):
+  provider: Provider,
-                           Future[?TransactionReceipt] {.base, gcsafe.} =
+  txHash: TransactionHash): Future[?TransactionReceipt] {.base, async: (raises:[ProviderError]).} =
+
   doAssert false, "not implemented"
 
-method sendTransaction*(provider: Provider,
+method sendTransaction*(
-                        rawTransaction: seq[byte]):
+  provider: Provider,
-                       Future[TransactionResponse] {.base, gcsafe.} =
+  rawTransaction: seq[byte]): Future[TransactionResponse] {.base, async: (raises:[ProviderError]).} =
+
   doAssert false, "not implemented"
 
-method getLogs*(provider: Provider,
+method getLogs*(
-                filter: EventFilter): Future[seq[Log]] {.base, gcsafe.} =
+  provider: Provider,
+  filter: EventFilter): Future[seq[Log]] {.base, async: (raises:[ProviderError]).} =
+
   doAssert false, "not implemented"
 
-method estimateGas*(provider: Provider,
+method estimateGas*(
+  provider: Provider,
   transaction: Transaction,
-                    blockTag = BlockTag.latest): Future[UInt256] {.base, gcsafe.} =
+  blockTag = BlockTag.latest): Future[UInt256] {.base, async: (raises:[ProviderError]).} =
+
   doAssert false, "not implemented"
 
-method getChainId*(provider: Provider): Future[UInt256] {.base, gcsafe.} =
+method getChainId*(
+  provider: Provider): Future[UInt256] {.base, async: (raises:[ProviderError]).} =
+
   doAssert false, "not implemented"
 
-method subscribe*(provider: Provider,
+method subscribe*(
+  provider: Provider,
   filter: EventFilter,
-                  callback: LogHandler):
+  callback: LogHandler): Future[Subscription] {.base, async: (raises:[ProviderError]).} =
-                 Future[Subscription] {.base, gcsafe.} =
+
   doAssert false, "not implemented"
 
-method subscribe*(provider: Provider,
+method subscribe*(
-                  callback: BlockHandler):
+  provider: Provider,
-                 Future[Subscription] {.base, gcsafe.} =
+  callback: BlockHandler): Future[Subscription] {.base, async: (raises:[ProviderError]).} =
+
   doAssert false, "not implemented"
 
-method unsubscribe*(subscription: Subscription) {.base, async.} =
+method unsubscribe*(
+  subscription: Subscription) {.base, async: (raises:[ProviderError]).} =
+
   doAssert false, "not implemented"
 
-proc replay*(provider: Provider, tx: Transaction, blockNumber: UInt256) {.async.} =
+proc replay*(
+  provider: Provider,
+  tx: Transaction,
+  blockNumber: UInt256) {.async: (raises:[ProviderError]).} =
   # Replay transaction at block. Useful for fetching revert reasons, which will
   # be present in the raised error message. The replayed block number should
   # include the state of the chain in the block previous to the block in which
@@ -171,8 +199,7 @@ proc replay*(provider: Provider, tx: Transaction, blockNumber: UInt256) {.async.
 method getRevertReason*(
   provider: Provider,
   hash: TransactionHash,
-  blockNumber: UInt256
+  blockNumber: UInt256): Future[?string] {.base, async: (raises: [ProviderError]).} =
-): Future[?string] {.base, async.} =
 
   without pastTx =? await provider.getTransaction(hash):
     return none string
@@ -186,8 +213,7 @@ method getRevertReason*(
 
 method getRevertReason*(
   provider: Provider,
-  receipt: TransactionReceipt
+  receipt: TransactionReceipt): Future[?string] {.base, async: (raises: [ProviderError]).} =
-): Future[?string] {.base, async.} =
 
   if receipt.status != TransactionStatus.Failure:
     return none string
@@ -199,8 +225,7 @@ method getRevertReason*(
 
 proc ensureSuccess(
   provider: Provider,
-  receipt: TransactionReceipt
+  receipt: TransactionReceipt) {.async: (raises: [ProviderError]).} =
-) {.async, raises: [ProviderError].} =
   ## If the receipt.status is Failed, the tx is replayed to obtain a revert
   ## reason, after which a ProviderError with the revert reason is raised.
   ## If no revert reason was obtained
@@ -219,11 +244,12 @@ proc ensureSuccess(
       trace "transaction replay completed, no revert reason obtained"
       raiseProviderError("Transaction reverted with unknown reason")
 
-proc confirm*(tx: TransactionResponse,
+proc confirm*(
+  tx: TransactionResponse,
   confirmations = EthersDefaultConfirmations,
-              timeout = EthersReceiptTimeoutBlks):
+  timeout = EthersReceiptTimeoutBlks): Future[TransactionReceipt]
-             Future[TransactionReceipt]
+  {.async: (raises: [CancelledError, ProviderError, EthersError]).} =
-             {.async, raises: [ProviderError, EthersError].} =
+
   ## Waits for a transaction to be mined and for the specified number of blocks
   ## to pass since it was mined (confirmations).
   ## A timeout, in blocks, can be specified that will raise an error if too many
@@ -265,10 +291,10 @@ proc confirm*(tx: TransactionResponse,
       await tx.provider.ensureSuccess(receipt)
       return receipt
 
-proc confirm*(tx: Future[TransactionResponse],
+proc confirm*(
+  tx: Future[TransactionResponse],
   confirmations: int = EthersDefaultConfirmations,
-             timeout: int = EthersReceiptTimeoutBlks):
+  timeout: int = EthersReceiptTimeoutBlks): Future[TransactionReceipt] {.async.} =
-            Future[TransactionReceipt] {.async.} =
   ## Convenience method that allows wait to be chained to a sendTransaction
   ## call, eg:
   ## `await signer.sendTransaction(populated).confirm(3)`
@@ -276,5 +302,5 @@ proc confirm*(tx: Future[TransactionResponse],
   let txResp = await tx
   return await txResp.confirm(confirmations, timeout)
 
-method close*(provider: Provider) {.async, base.} =
+method close*(provider: Provider) {.base, async: (raises:[ProviderError]).} =
   discard

ethers/providers/jsonrpc.nim

@@ -1,10 +1,10 @@
-import std/json
 import std/tables
 import std/uri
 import pkg/chronicles
 import pkg/eth/common/eth_types_json_serialization
 import pkg/json_rpc/rpcclient
 import pkg/json_rpc/errors
+import pkg/serde
 import ../basics
 import ../provider
 import ../signer
@@ -12,7 +12,6 @@ import ./jsonrpc/rpccalls
 import ./jsonrpc/conversions
 import ./jsonrpc/subscriptions
 
-export json
 export basics
 export provider
 export chronicles
@@ -26,20 +25,25 @@ type
   JsonRpcProvider* = ref object of Provider
     client: Future[RpcClient]
     subscriptions: Future[JsonRpcSubscriptions]
-  JsonRpcSigner* = ref object of Signer
+
-    provider: JsonRpcProvider
-    address: ?Address
   JsonRpcProviderError* = object of ProviderError
   JsonRpcSubscription* = ref object of Subscription
     subscriptions: JsonRpcSubscriptions
     id: JsonNode
 
-proc raiseJsonRpcProviderError(message: string) {.raises: [JsonRpcProviderError].} =
+  # Signer
+  JsonRpcSigner* = ref object of Signer
+    provider: JsonRpcProvider
+    address: ?Address
+  JsonRpcSignerError* = object of SignerError
+
+proc raiseJsonRpcProviderError(
+  message: string) {.raises: [JsonRpcProviderError].} =
+
   var message = message
-  try:
+  if json =? JsonNode.fromJson(message):
-    message = parseJson(message){"message"}.getStr
+    if "message" in json:
-  except Exception:
+      message = json{"message"}.getStr
-    discard
   raise newException(JsonRpcProviderError, message)
 
 template convertError(body) =
@@ -47,9 +51,7 @@ template convertError(body) =
     body
   except JsonRpcError as error:
     raiseJsonRpcProviderError(error.msg)
-  # Catch all ValueErrors for now, at least until JsonRpcError is actually
+  except CatchableError as error:
-  # raised. PR created: https://github.com/status-im/nim-json-rpc/pull/151
-  except ValueError as error:
     raiseJsonRpcProviderError(error.msg)
 
 # Provider
@@ -60,14 +62,17 @@ const defaultPollingInterval = 4.seconds
 proc jsonHeaders: seq[(string, string)] =
   @[("Content-Type", "application/json")]
 
-proc new*(_: type JsonRpcProvider,
+proc new*(
+  _: type JsonRpcProvider,
   url=defaultUrl,
-          pollingInterval=defaultPollingInterval): JsonRpcProvider =
+  pollingInterval=defaultPollingInterval): JsonRpcProvider {.raises: [JsonRpcProviderError].} =
+
   var initialized: Future[void]
   var client: RpcClient
   var subscriptions: JsonRpcSubscriptions
 
-  proc initialize {.async.} =
+  proc initialize {.async: (raises:[JsonRpcProviderError]).} =
+    convertError:
       case parseUri(url).scheme
       of "ws", "wss":
         let websocket = newRpcWebSocketClient(getHeaders = jsonHeaders)
@@ -80,28 +85,45 @@ proc new*(_: type JsonRpcProvider,
         client = http
         subscriptions = JsonRpcSubscriptions.new(http,
                                                 pollingInterval = pollingInterval)
+      subscriptions.start()
 
-  proc awaitClient: Future[RpcClient] {.async.} =
+  proc awaitClient: Future[RpcClient] {.async:(raises:[JsonRpcProviderError]).} =
     convertError:
       await initialized
       return client
 
-  proc awaitSubscriptions: Future[JsonRpcSubscriptions] {.async.} =
+  proc awaitSubscriptions: Future[JsonRpcSubscriptions] {.async:(raises:[JsonRpcProviderError]).} =
     convertError:
       await initialized
       return subscriptions
 
   initialized = initialize()
-  JsonRpcProvider(client: awaitClient(), subscriptions: awaitSubscriptions())
+  return JsonRpcProvider(client: awaitClient(), subscriptions: awaitSubscriptions())
 
-proc send*(provider: JsonRpcProvider,
+proc callImpl(
+  client: RpcClient,
   call: string,
-           arguments: seq[JsonNode] = @[]): Future[JsonNode] {.async.} =
+  args: JsonNode): Future[JsonNode] {.async: (raises: [JsonRpcProviderError]).} =
+
+  without response =? (await client.call(call, %args)).catch, error:
+    raiseJsonRpcProviderError error.msg
+  without json =? JsonNode.fromJson(response.string), error:
+    raiseJsonRpcProviderError "Failed to parse response: " & error.msg
+  json
+
+proc send*(
+  provider: JsonRpcProvider,
+  call: string,
+  arguments: seq[JsonNode] = @[]): Future[JsonNode]
+  {.async: (raises: [JsonRpcProviderError]).} =
+
   convertError:
     let client = await provider.client
-    return await client.call(call, %arguments)
+    return await client.callImpl(call, %arguments)
+
+proc listAccounts*(provider: JsonRpcProvider): Future[seq[Address]]
+  {.async: (raises: [JsonRpcProviderError]).} =
 
-proc listAccounts*(provider: JsonRpcProvider): Future[seq[Address]] {.async.} =
   convertError:
     let client = await provider.client
     return await client.eth_accounts()
@@ -112,54 +134,66 @@ proc getSigner*(provider: JsonRpcProvider): JsonRpcSigner =
 proc getSigner*(provider: JsonRpcProvider, address: Address): JsonRpcSigner =
   JsonRpcSigner(provider: provider, address: some address)
 
-method getBlockNumber*(provider: JsonRpcProvider): Future[UInt256] {.async.} =
+method getBlockNumber*(
+  provider: JsonRpcProvider): Future[UInt256] {.async: (raises:[ProviderError]).} =
+
   convertError:
     let client = await provider.client
     return await client.eth_blockNumber()
 
-method getBlock*(provider: JsonRpcProvider,
+method getBlock*(
-                 tag: BlockTag): Future[?Block] {.async.} =
+  provider: JsonRpcProvider,
+  tag: BlockTag): Future[?Block] {.async: (raises:[ProviderError]).} =
+
   convertError:
     let client = await provider.client
     return await client.eth_getBlockByNumber(tag, false)
 
-method call*(provider: JsonRpcProvider,
+method call*(
+  provider: JsonRpcProvider,
   tx: Transaction,
-             blockTag = BlockTag.latest): Future[seq[byte]] {.async.} =
+  blockTag = BlockTag.latest): Future[seq[byte]] {.async: (raises:[ProviderError]).} =
+
   convertError:
     let client = await provider.client
     return await client.eth_call(tx, blockTag)
 
-method getGasPrice*(provider: JsonRpcProvider): Future[UInt256] {.async.} =
+method getGasPrice*(
+  provider: JsonRpcProvider): Future[UInt256] {.async: (raises:[ProviderError]).} =
+
   convertError:
     let client = await provider.client
     return await client.eth_gasPrice()
 
-method getTransactionCount*(provider: JsonRpcProvider,
+method getTransactionCount*(
+  provider: JsonRpcProvider,
   address: Address,
-                            blockTag = BlockTag.latest):
+  blockTag = BlockTag.latest): Future[UInt256] {.async: (raises:[ProviderError]).} =
-                           Future[UInt256] {.async.} =
+
   convertError:
     let client = await provider.client
     return await client.eth_getTransactionCount(address, blockTag)
 
-method getTransaction*(provider: JsonRpcProvider,
+method getTransaction*(
-                       txHash: TransactionHash):
+  provider: JsonRpcProvider,
-                      Future[?PastTransaction] {.async.} =
+  txHash: TransactionHash): Future[?PastTransaction] {.async: (raises:[ProviderError]).} =
+
   convertError:
     let client = await provider.client
     return await client.eth_getTransactionByHash(txHash)
 
-method getTransactionReceipt*(provider: JsonRpcProvider,
+method getTransactionReceipt*(
-                              txHash: TransactionHash):
+  provider: JsonRpcProvider,
-                             Future[?TransactionReceipt] {.async.} =
+  txHash: TransactionHash): Future[?TransactionReceipt] {.async: (raises:[ProviderError]).} =
+
   convertError:
     let client = await provider.client
     return await client.eth_getTransactionReceipt(txHash)
 
-method getLogs*(provider: JsonRpcProvider,
+method getLogs*(
-                filter: EventFilter):
+  provider: JsonRpcProvider,
-               Future[seq[Log]] {.async.} =
+  filter: EventFilter): Future[seq[Log]] {.async: (raises:[ProviderError]).} =
+
   convertError:
     let client = await provider.client
     let logsJson = if filter of Filter:
@@ -171,19 +205,23 @@ method getLogs*(provider: JsonRpcProvider,
 
     var logs: seq[Log] = @[]
     for logJson in logsJson.getElems:
-      if log =? Log.fromJson(logJson).catch:
+      if log =? Log.fromJson(logJson):
         logs.add log
 
     return logs
 
-method estimateGas*(provider: JsonRpcProvider,
+method estimateGas*(
+  provider: JsonRpcProvider,
   transaction: Transaction,
-                    blockTag = BlockTag.latest): Future[UInt256] {.async.} =
+  blockTag = BlockTag.latest): Future[UInt256] {.async: (raises:[ProviderError]).} =
+
   convertError:
     let client = await provider.client
     return await client.eth_estimateGas(transaction, blockTag)
 
-method getChainId*(provider: JsonRpcProvider): Future[UInt256] {.async.} =
+method getChainId*(
+  provider: JsonRpcProvider): Future[UInt256] {.async: (raises:[ProviderError]).} =
+
   convertError:
     let client = await provider.client
     try:
@@ -191,7 +229,11 @@ method getChainId*(provider: JsonRpcProvider): Future[UInt256] {.async.} =
     except CatchableError:
       return parse(await client.net_version(), UInt256)
 
-method sendTransaction*(provider: JsonRpcProvider, rawTransaction: seq[byte]): Future[TransactionResponse] {.async.} =
+method sendTransaction*(
+  provider: JsonRpcProvider,
+  rawTransaction: seq[byte]): Future[TransactionResponse]
+  {.async: (raises:[ProviderError]).} =
+
   convertError:
     let
       client = await provider.client
@@ -199,30 +241,36 @@ method sendTransaction*(provider: JsonRpcProvider, rawTransaction: seq[byte]): F
 
     return TransactionResponse(hash: hash, provider: provider)
 
-method subscribe*(provider: JsonRpcProvider,
+method subscribe*(
+  provider: JsonRpcProvider,
   filter: EventFilter,
-                  onLog: LogHandler):
+  onLog: LogHandler): Future[Subscription] {.async: (raises:[ProviderError]).} =
-                 Future[Subscription] {.async.} =
+
   convertError:
     let subscriptions = await provider.subscriptions
     let id = await subscriptions.subscribeLogs(filter, onLog)
     return JsonRpcSubscription(subscriptions: subscriptions, id: id)
 
-method subscribe*(provider: JsonRpcProvider,
+method subscribe*(
-                  onBlock: BlockHandler):
+  provider: JsonRpcProvider,
-                 Future[Subscription] {.async.} =
+  onBlock: BlockHandler): Future[Subscription] {.async: (raises:[ProviderError]).} =
+
   convertError:
     let subscriptions = await provider.subscriptions
     let id = await subscriptions.subscribeBlocks(onBlock)
     return JsonRpcSubscription(subscriptions: subscriptions, id: id)
 
-method unsubscribe(subscription: JsonRpcSubscription) {.async.} =
+method unsubscribe*(
+  subscription: JsonRpcSubscription) {.async: (raises:[ProviderError]).} =
+
   convertError:
     let subscriptions = subscription.subscriptions
     let id = subscription.id
     await subscriptions.unsubscribe(id)
 
-method close*(provider: JsonRpcProvider) {.async.} =
+method close*(
+  provider: JsonRpcProvider) {.async: (raises:[ProviderError]).} =
+
   convertError:
     let client = await provider.client
     let subscriptions = await provider.subscriptions
@@ -231,10 +279,32 @@ method close*(provider: JsonRpcProvider) {.async.} =
 
 # Signer
 
-method provider*(signer: JsonRpcSigner): Provider =
+proc raiseJsonRpcSignerError(
+  message: string) {.raises: [JsonRpcSignerError].} =
+
+  var message = message
+  if json =? JsonNode.fromJson(message):
+    if "message" in json:
+      message = json{"message"}.getStr
+  raise newException(JsonRpcSignerError, message)
+
+template convertSignerError(body) =
+  try:
+    body
+  except JsonRpcError as error:
+    raiseJsonRpcSignerError(error.msg)
+  except CatchableError as error:
+    raise newException(JsonRpcSignerError, error.msg)
+
+method provider*(signer: JsonRpcSigner): Provider
+  {.gcsafe, raises: [SignerError].} =
+
   signer.provider
 
-method getAddress*(signer: JsonRpcSigner): Future[Address] {.async.} =
+method getAddress*(
+  signer: JsonRpcSigner): Future[Address]
+  {.async: (raises:[ProviderError, SignerError]).} =
+
   if address =? signer.address:
     return address
 
@@ -242,18 +312,23 @@ method getAddress*(signer: JsonRpcSigner): Future[Address] {.async.} =
   if accounts.len > 0:
     return accounts[0]
 
-  raiseJsonRpcProviderError "no address found"
+  raiseJsonRpcSignerError "no address found"
 
-method signMessage*(signer: JsonRpcSigner,
+method signMessage*(
-                    message: seq[byte]): Future[seq[byte]] {.async.} =
+  signer: JsonRpcSigner,
-  convertError:
+  message: seq[byte]): Future[seq[byte]] {.async: (raises:[SignerError]).} =
+
+  convertSignerError:
     let client = await signer.provider.client
     let address = await signer.getAddress()
     return await client.eth_sign(address, message)
 
-method sendTransaction*(signer: JsonRpcSigner,
+method sendTransaction*(
-                        transaction: Transaction): Future[TransactionResponse] {.async.} =
+  signer: JsonRpcSigner,
-  convertError:
+  transaction: Transaction): Future[TransactionResponse]
+  {.async: (raises:[SignerError]).} =
+
+  convertSignerError:
     if nonce =? transaction.nonce:
       signer.updateNonce(nonce)
     let

ethers/providers/jsonrpc/conversions.nim

@@ -1,7 +1,9 @@
-import std/json
 import std/strformat
 import std/strutils
+import pkg/chronicles except fromJson, `%`, `%*`, toJson
 import pkg/json_rpc/jsonmarshal
+import pkg/questionable/results
+import pkg/serde
 import pkg/stew/byteutils
 import ../../basics
 import ../../transaction
@@ -9,68 +11,57 @@ import ../../blocktag
 import ../../provider
 
 export jsonmarshal
+export serde
+export chronicles except fromJson, `%`, `%*`, toJson
 
-type JsonSerializationError = object of EthersError
+{.push raises: [].}
 
-template raiseSerializationError(message: string) =
+proc getOrRaise*[T, E](self: ?!T, exc: typedesc[E]): T {.raises: [E].} =
-  raise newException(JsonSerializationError, message)
+  let val = self.valueOr:
+    raise newException(E, self.error.msg)
+  val
 
-proc expectFields(json: JsonNode, expectedFields: varargs[string]) =
+template mapFailure*[T, V, E](
-  for fieldName in expectedFields:
+    exp: Result[T, V],
-    if not json.hasKey(fieldName):
+    exc: typedesc[E],
-      raiseSerializationError(fmt"'{fieldName}' field not found in ${json}")
+): Result[T, ref CatchableError] =
+  ## Convert `Result[T, E]` to `Result[E, ref CatchableError]`
+  ##
 
-func fromJson*(T: type, json: JsonNode, name = ""): T =
+  exp.mapErr(proc (e: V): ref CatchableError = (ref exc)(msg: e.msg))
-  fromJson(json, name, result)
-
-# byte sequence
-
-func `%`*(bytes: seq[byte]): JsonNode =
-  %("0x" & bytes.toHex)
-
-func fromJson*(json: JsonNode, name: string, result: var seq[byte]) =
-  result = hexToSeqByte(json.getStr())
-
-# byte arrays
-
-func `%`*[N](bytes: array[N, byte]): JsonNode =
-  %("0x" & bytes.toHex)
-
-func fromJson*[N](json: JsonNode, name: string, result: var array[N, byte]) =
-  hexToByteArray(json.getStr(), result)
 
 # Address
 
 func `%`*(address: Address): JsonNode =
   %($address)
 
-func fromJson*(json: JsonNode, name: string, result: var Address) =
+func fromJson(_: type Address, json: JsonNode): ?!Address =
-  if address =? Address.init(json.getStr()):
+  expectJsonKind(Address, JString, json)
-    result = address
+  without address =? Address.init(json.getStr), error:
-  else:
+    return failure newException(SerializationError,
-    raise newException(ValueError, "\""  & name & "\"is not an Address")
+      "Failed to convert '" & $json & "' to Address: " & error.msg)
+  success address
 
 # UInt256
 
 func `%`*(integer: UInt256): JsonNode =
   %("0x" & toHex(integer))
 
-func fromJson*(json: JsonNode, name: string, result: var UInt256) =
+func fromJson*(_: type UInt256, json: JsonNode): ?!UInt256 =
-  result = UInt256.fromHex(json.getStr())
+  without result =? UInt256.fromHex(json.getStr()).catch, error:
-
+    return UInt256.failure error.msg
-# TransactionType
+  success result
-
-func fromJson*(json: JsonNode, name: string, result: var TransactionType) =
-  let val = fromHex[int](json.getStr)
-  result = TransactionType(val)
-
-func `%`*(txType: TransactionType): JsonNode =
-  %("0x" & txType.int.toHex(1))
 
 # Transaction
 
+# TODO: add option that ignores none Option[T]
+# TODO: add name option (gasLimit => gas, sender => from)
 func `%`*(transaction: Transaction): JsonNode =
-  result = %{ "to": %transaction.to, "data": %transaction.data }
+  result = %*{
+    "to": transaction.to,
+    "data": %transaction.data,
+    "value": %transaction.value
+  }
   if sender =? transaction.sender:
     result["from"] = %sender
   if nonce =? transaction.nonce:
@@ -84,105 +75,52 @@ func `%`*(transaction: Transaction): JsonNode =
 
 # BlockTag
 
-func `%`*(blockTag: BlockTag): JsonNode =
+func `%`*(tag: BlockTag): JsonNode =
-  %($blockTag)
+  % $tag
 
-# Log
+func fromJson*(_: type BlockTag, json: JsonNode): ?!BlockTag =
+  expectJsonKind(BlockTag, JString, json)
+  let jsonVal = json.getStr
+  if jsonVal[0..1].toLowerAscii == "0x":
+    without blkNum =? UInt256.fromHex(jsonVal).catch, error:
+      return BlockTag.failure error.msg
+    return success BlockTag.init(blkNum)
 
-func fromJson*(json: JsonNode, name: string, result: var Log) =
+  case jsonVal:
-  if not (json.hasKey("data") and json.hasKey("topics")):
+  of "earliest": return success BlockTag.earliest
-    raise newException(ValueError, "'data' and/or 'topics' fields not found")
+  of "latest": return success BlockTag.latest
+  of "pending": return success BlockTag.pending
+  else: return failure newException(SerializationError,
+      "Failed to convert '" & $json &
+      "' to BlockTag: must be one of 'earliest', 'latest', 'pending'")
 
-  var data: seq[byte]
+# TransactionStatus | TransactionType
-  var topics: seq[Topic]
-  fromJson(json["data"], "data", data)
-  fromJson(json["topics"], "topics", topics)
-  result = Log(data: data, topics: topics)
 
-# TransactionStatus
+func `%`*(e: TransactionStatus | TransactionType): JsonNode =
+  % ("0x" & e.int8.toHex(1))
 
-func fromJson*(json: JsonNode, name: string, result: var TransactionStatus) =
+proc fromJson*[E: TransactionStatus | TransactionType](
-  let val = fromHex[int](json.getStr)
+  T: type E,
-  result = TransactionStatus(val)
+  json: JsonNode
+): ?!T =
+  expectJsonKind(string, JString, json)
+  let integer = ? fromHex[int](json.str).catch.mapFailure(SerializationError)
+  success T(integer)
 
-func `%`*(status: TransactionStatus): JsonNode =
+## Generic conversions to use nim-json instead of nim-json-serialization for
-  %("0x" & status.int.toHex(1))
+## json rpc serialization purposes
+##  writeValue => `%`
+##  readValue  => fromJson
 
-# PastTransaction
+proc writeValue*[T: not JsonNode](
+  writer: var JsonWriter[JrpcConv],
+  value: T) {.raises:[IOError].} =
 
-func fromJson*(json: JsonNode, name: string, result: var PastTransaction) =
+  writer.writeValue(%value)
-  # Deserializes a past transaction, eg eth_getTransactionByHash.
-  # Spec: https://ethereum.org/en/developers/docs/apis/json-rpc/#eth_gettransactionbyhash
-  json.expectFields "blockHash", "blockNumber", "from", "gas", "gasPrice",
-                    "hash", "input", "nonce", "to", "transactionIndex", "value",
-                    "v", "r", "s"
 
-  result = PastTransaction(
+proc readValue*[T: not JsonNode](
-    blockHash: BlockHash.fromJson(json["blockHash"], "blockHash"),
+  r: var JsonReader[JrpcConv],
-    blockNumber: UInt256.fromJson(json["blockNumber"], "blockNumber"),
+  result: var T) {.raises: [SerializationError, IOError].} =
-    sender: Address.fromJson(json["from"], "from"),
-    gas: UInt256.fromJson(json["gas"], "gas"),
-    gasPrice: UInt256.fromJson(json["gasPrice"], "gasPrice"),
-    hash: TransactionHash.fromJson(json["hash"], "hash"),
-    input: seq[byte].fromJson(json["input"], "input"),
-    nonce: UInt256.fromJson(json["nonce"], "nonce"),
-    to: Address.fromJson(json["to"], "to"),
-    transactionIndex: UInt256.fromJson(json["transactionIndex"], "transactionIndex"),
-    value: UInt256.fromJson(json["value"], "value"),
-    v: UInt256.fromJson(json["v"], "v"),
-    r: UInt256.fromJson(json["r"], "r"),
-    s: UInt256.fromJson(json["s"], "s"),
-  )
-  if json.hasKey("type"):
-    result.transactionType = fromJson(?TransactionType, json["type"], "type")
-  if json.hasKey("chainId"):
-    result.chainId = fromJson(?UInt256, json["chainId"], "chainId")
 
-func `%`*(tx: PastTransaction): JsonNode =
+  var json = r.readValue(JsonNode)
-  let json = %*{
+  result = T.fromJson(json).getOrRaise(SerializationError)
-    "blockHash": tx.blockHash,
-    "blockNumber": tx.blockNumber,
-    "from": tx.sender,
-    "gas": tx.gas,
-    "gasPrice": tx.gasPrice,
-    "hash": tx.hash,
-    "input": tx.input,
-    "nonce": tx.nonce,
-    "to": tx.to,
-    "transactionIndex": tx.transactionIndex,
-    "value": tx.value,
-    "v": tx.v,
-    "r": tx.r,
-    "s": tx.s
-  }
-  if txType =? tx.transactionType:
-    json["type"] = %txType
-  if chainId =? tx.chainId:
-    json["chainId"] = %chainId
-  return json
-
-# TransactionReceipt
-
-func fromJson*(json: JsonNode, name: string, result: var TransactionReceipt) =
-  # Deserializes a transaction receipt, eg eth_getTransactionReceipt.
-  # Spec: https://ethereum.org/en/developers/docs/apis/json-rpc/#eth_gettransactionreceipt
-  json.expectFields "transactionHash", "transactionIndex", "cumulativeGasUsed",
-                    "effectiveGasPrice", "gasUsed", "logs", "logsBloom", "type",
-                    "status"
-
-  result = TransactionReceipt(
-    transactionHash: fromJson(TransactionHash, json["transactionHash"], "transactionHash"),
-    transactionIndex: UInt256.fromJson(json["transactionIndex"], "transactionIndex"),
-    blockHash: fromJson(?BlockHash, json["blockHash"], "blockHash"),
-    blockNumber: fromJson(?UInt256, json["blockNumber"], "blockNumber"),
-    sender: fromJson(?Address, json["from"], "from"),
-    to: fromJson(?Address, json["to"], "to"),
-    cumulativeGasUsed: UInt256.fromJson(json["cumulativeGasUsed"], "cumulativeGasUsed"),
-    effectiveGasPrice: fromJson(?UInt256, json["effectiveGasPrice"], "effectiveGasPrice"),
-    gasUsed: UInt256.fromJson(json["gasUsed"], "gasUsed"),
-    contractAddress: fromJson(?Address, json["contractAddress"], "contractAddress"),
-    logs: seq[Log].fromJson(json["logs"], "logs"),
-    logsBloom: seq[byte].fromJson(json["logsBloom"], "logsBloom"),
-    transactionType: TransactionType.fromJson(json["type"], "type"),
-    status: TransactionStatus.fromJson(json["status"], "status")
-  )

ethers/providers/jsonrpc/looping.nim

@@ -2,5 +2,5 @@ template untilCancelled*(body) =
   try:
     while true:
       body
-  except CancelledError:
+  except CancelledError as e:
-    raise
+    raise e

ethers/providers/jsonrpc/subscriptions.nim

@@ -4,6 +4,7 @@ import pkg/chronos
 import pkg/json_rpc/rpcclient
 import ../../basics
 import ../../provider
+include ../../nimshims/hashes
 import ./rpccalls
 import ./conversions
 import ./looping
@@ -12,8 +13,41 @@ type
   JsonRpcSubscriptions* = ref object of RootObj
     client: RpcClient
     callbacks: Table[JsonNode, SubscriptionCallback]
+    methodHandlers: Table[string, MethodHandler]
+  MethodHandler* = proc (j: JsonNode) {.gcsafe, raises: [].}
   SubscriptionCallback = proc(id, arguments: JsonNode) {.gcsafe, raises:[].}
 
+{.push raises:[].}
+
+template `or`(a: JsonNode, b: typed): JsonNode =
+  if a.isNil: b else: a
+
+func start*(subscriptions: JsonRpcSubscriptions) =
+  subscriptions.client.onProcessMessage =
+    proc(client: RpcClient,
+         line: string): Result[bool, string] {.gcsafe, raises: [].} =
+      if json =? JsonNode.fromJson(line):
+        if "method" in json:
+          let methodName = json{"method"}.getStr()
+          if methodName in subscriptions.methodHandlers:
+            let handler = subscriptions.methodHandlers.getOrDefault(methodName)
+            if not handler.isNil:
+              handler(json{"params"} or newJArray())
+              # false = do not continue processing message using json_rpc's
+              # default processing handler
+              return ok false
+
+      # true = continue processing message using json_rpc's default message handler
+      return ok true
+
+
+proc setMethodHandler(
+  subscriptions: JsonRpcSubscriptions,
+  `method`: string,
+  handler: MethodHandler
+) =
+  subscriptions.methodHandlers[`method`] = handler
+
 method subscribeBlocks*(subscriptions: JsonRpcSubscriptions,
                         onBlock: BlockHandler):
                        Future[JsonNode]
@@ -40,11 +74,11 @@ method close*(subscriptions: JsonRpcSubscriptions) {.async, base.} =
 proc getCallback(subscriptions: JsonRpcSubscriptions,
                  id: JsonNode): ?SubscriptionCallback =
   try:
-    if subscriptions.callbacks.hasKey(id):
+    if not id.isNil and id in subscriptions.callbacks:
       subscriptions.callbacks[id].some
     else:
       SubscriptionCallback.none
-  except Exception:
+  except KeyError:
     SubscriptionCallback.none
 
 # Web sockets
@@ -54,20 +88,21 @@ type
 
 proc new*(_: type JsonRpcSubscriptions,
           client: RpcWebSocketClient): JsonRpcSubscriptions =
+
   let subscriptions = WebSocketSubscriptions(client: client)
   proc subscriptionHandler(arguments: JsonNode) {.raises:[].} =
-    if id =? arguments["subscription"].catch and
+    let id = arguments{"subscription"} or newJString("")
-       callback =? subscriptions.getCallback(id):
+    if callback =? subscriptions.getCallback(id):
       callback(id, arguments)
-  client.setMethodHandler("eth_subscription", subscriptionHandler)
+  subscriptions.setMethodHandler("eth_subscription", subscriptionHandler)
   subscriptions
 
 method subscribeBlocks(subscriptions: WebSocketSubscriptions,
                        onBlock: BlockHandler):
                       Future[JsonNode]
                       {.async.} =
-  proc callback(id, arguments: JsonNode) =
+  proc callback(id, arguments: JsonNode) {.raises: [].} =
-    if blck =? Block.fromJson(arguments["result"]).catch:
+    if blck =? Block.fromJson(arguments{"result"}):
       onBlock(blck)
   let id = await subscriptions.client.eth_subscribe("newHeads")
   subscriptions.callbacks[id] = callback
@@ -79,13 +114,13 @@ method subscribeLogs(subscriptions: WebSocketSubscriptions,
                     Future[JsonNode]
                     {.async.} =
   proc callback(id, arguments: JsonNode) =
-    if log =? Log.fromJson(arguments["result"]).catch:
+    if log =? Log.fromJson(arguments{"result"}):
       onLog(log)
   let id = await subscriptions.client.eth_subscribe("logs", filter)
   subscriptions.callbacks[id] = callback
   return id
 
-method unsubscribe(subscriptions: WebSocketSubscriptions,
+method unsubscribe*(subscriptions: WebSocketSubscriptions,
                    id: JsonNode)
                   {.async.} =
   subscriptions.callbacks.del(id)
@@ -140,7 +175,7 @@ method subscribeBlocks(subscriptions: PollingSubscriptions,
       discard
 
   proc callback(id, change: JsonNode) =
-    if hash =? BlockHash.fromJson(change).catch:
+    if hash =? BlockHash.fromJson(change):
       asyncSpawn getBlock(hash)
 
   let id = await subscriptions.client.eth_newBlockFilter()
@@ -154,14 +189,14 @@ method subscribeLogs(subscriptions: PollingSubscriptions,
                     {.async.} =
 
   proc callback(id, change: JsonNode) =
-    if log =? Log.fromJson(change).catch:
+    if log =? Log.fromJson(change):
       onLog(log)
 
   let id = await subscriptions.client.eth_newFilter(filter)
   subscriptions.callbacks[id] = callback
   return id
 
-method unsubscribe(subscriptions: PollingSubscriptions,
+method unsubscribe*(subscriptions: PollingSubscriptions,
                    id: JsonNode)
                   {.async.} =
   subscriptions.callbacks.del(id)

ethers/signer.nim

@@ -1,14 +1,15 @@
+import pkg/questionable
 import ./basics
 import ./provider
 
 export basics
 
+{.push raises: [].}
+
 type
   Signer* = ref object of RootObj
     lastSeenNonce: ?UInt256
     populateLock: AsyncLock
-
-type
   SignerError* = object of EthersError
   EstimateGasError* = object of SignerError
     transaction*: Transaction
@@ -19,50 +20,87 @@ template raiseSignerError(message: string, parent: ref ProviderError = nil) =
 proc raiseEstimateGasError(
   transaction: Transaction,
   parent: ref ProviderError = nil
-) =
+) {.raises: [EstimateGasError] .} =
   let e = (ref EstimateGasError)(
     msg: "Estimate gas failed",
     transaction: transaction,
     parent: parent)
   raise e
 
-method provider*(signer: Signer): Provider {.base, gcsafe.} =
+template convertError(body) =
+  try:
+    body
+  except EthersError as error:
+    raiseSignerError(error.msg)
+  except CatchableError as error:
+    raiseSignerError(error.msg)
+
+method provider*(
+  signer: Signer): Provider {.base, gcsafe, raises: [SignerError].} =
   doAssert false, "not implemented"
 
-method getAddress*(signer: Signer): Future[Address] {.base, gcsafe.} =
+method getAddress*(
+  signer: Signer): Future[Address]
+  {.base, async: (raises:[ProviderError, SignerError]).} =
+
   doAssert false, "not implemented"
 
-method signMessage*(signer: Signer,
+method signMessage*(
-                    message: seq[byte]): Future[seq[byte]] {.base, async.} =
+  signer: Signer,
+  message: seq[byte]): Future[seq[byte]]
+  {.base, async: (raises: [SignerError]).} =
+
   doAssert false, "not implemented"
 
-method sendTransaction*(signer: Signer,
+method sendTransaction*(
-                        transaction: Transaction): Future[TransactionResponse] {.base, async.} =
+  signer: Signer,
+  transaction: Transaction): Future[TransactionResponse]
+  {.base, async: (raises:[SignerError]).} =
+
   doAssert false, "not implemented"
 
-method getGasPrice*(signer: Signer): Future[UInt256] {.base, gcsafe.} =
+method getGasPrice*(
-  signer.provider.getGasPrice()
+  signer: Signer): Future[UInt256]
+  {.base, async: (raises: [ProviderError, SignerError]).} =
 
-method getTransactionCount*(signer: Signer,
+  return await signer.provider.getGasPrice()
-                            blockTag = BlockTag.latest):
+
-                           Future[UInt256] {.base, async.} =
+method getTransactionCount*(
+  signer: Signer,
+  blockTag = BlockTag.latest): Future[UInt256]
+  {.base, async: (raises:[SignerError]).} =
+
+  convertError:
     let address = await signer.getAddress()
     return await signer.provider.getTransactionCount(address, blockTag)
 
-method estimateGas*(signer: Signer,
+method estimateGas*(
+  signer: Signer,
   transaction: Transaction,
-                    blockTag = BlockTag.latest): Future[UInt256] {.base, async.} =
+  blockTag = BlockTag.latest): Future[UInt256]
+  {.base, async: (raises:[SignerError]).} =
+
   var transaction = transaction
-  transaction.sender = some(await signer.getAddress)
+  var address: Address
+
+  convertError:
+    address = await signer.getAddress
+
+  transaction.sender = some(address)
   try:
     return await signer.provider.estimateGas(transaction)
   except ProviderError as e:
     raiseEstimateGasError transaction, e
 
-method getChainId*(signer: Signer): Future[UInt256] {.base, gcsafe.} =
+method getChainId*(
-  signer.provider.getChainId()
+  signer: Signer): Future[UInt256]
+  {.base, async: (raises: [ProviderError, SignerError]).} =
+
+  return await signer.provider.getChainId()
+
+method getNonce(
+  signer: Signer): Future[UInt256] {.base, async: (raises: [SignerError]).} =
 
-method getNonce(signer: Signer): Future[UInt256] {.base, gcsafe, async.} =
   var nonce = await signer.getTransactionCount(BlockTag.pending)
 
   if lastSeen =? signer.lastSeenNonce and lastSeen >= nonce:
@@ -87,11 +125,16 @@ method decreaseNonce*(signer: Signer) {.base, gcsafe.} =
   if lastSeen =? signer.lastSeenNonce and lastSeen > 0:
     signer.lastSeenNonce = some lastSeen - 1
 
-method populateTransaction*(signer: Signer,
+method populateTransaction*(
-                            transaction: Transaction):
+  signer: Signer,
-                           Future[Transaction] {.base, async.} =
+  transaction: Transaction): Future[Transaction]
+  {.base, async: (raises: [CancelledError, AsyncLockError, ProviderError, SignerError]).} =
 
-  if sender =? transaction.sender and sender != await signer.getAddress():
+  var address: Address
+  convertError:
+    address = await signer.getAddress()
+
+  if sender =? transaction.sender and sender != address:
     raiseSignerError("from address mismatch")
   if chainId =? transaction.chainId and chainId != await signer.getChainId():
     raiseSignerError("chain id mismatch")
@@ -105,7 +148,7 @@ method populateTransaction*(signer: Signer,
 
   try:
     if transaction.sender.isNone:
-      populated.sender = some(await signer.getAddress())
+      populated.sender = some(address)
     if transaction.chainId.isNone:
       populated.chainId = some(await signer.getChainId())
     if transaction.gasPrice.isNone and (transaction.maxFee.isNone or transaction.maxPriorityFee.isNone):
@@ -119,10 +162,12 @@ method populateTransaction*(signer: Signer,
       populated.nonce = some(await signer.getNonce())
       try:
         populated.gasLimit = some(await signer.estimateGas(populated))
-      except ProviderError, EstimateGasError:
+      except EstimateGasError as e:
-        let e = getCurrentException()
         signer.decreaseNonce()
         raise e
+      except ProviderError as e:
+        signer.decreaseNonce()
+        raiseSignerError(e.msg)
 
     else:
       if transaction.nonce.isNone:
@@ -138,7 +183,7 @@ method populateTransaction*(signer: Signer,
 method cancelTransaction*(
   signer: Signer,
   tx: Transaction
-): Future[TransactionResponse] {.async, base.} =
+): Future[TransactionResponse] {.base, async: (raises: [SignerError]).} =
   # cancels a transaction by sending with a 0-valued transaction to ourselves
   # with the failed tx's nonce
 
@@ -148,5 +193,6 @@ method cancelTransaction*(
     raiseSignerError "transaction must have nonce"
 
   var cancelTx = Transaction(to: sender, value: 0.u256, nonce: some nonce)
+  convertError:
     cancelTx = await signer.populateTransaction(cancelTx)
     return await signer.sendTransaction(cancelTx)

ethers/signers/jsonrpc.nim

@@ -0,0 +1,3 @@
+import ../providers/jsonrpc
+
+export provider, getAddress, signMessage, sendTransaction

ethers/signers/wallet.nim

@@ -0,0 +1,92 @@
+import eth/keys
+import ../basics
+import ../provider
+import ../transaction
+import ../signer
+import ./wallet/error
+import ./wallet/signing
+
+export keys
+export WalletError
+export signing
+
+{.push raises: [].}
+
+var rng {.threadvar.}: ref HmacDrbgContext
+
+proc getRng: ref HmacDrbgContext =
+  if rng.isNil:
+    rng = newRng()
+  rng
+
+type Wallet* = ref object of Signer
+  privateKey*: PrivateKey
+  publicKey*: PublicKey
+  address*: Address
+  provider*: ?Provider
+
+proc new*(_: type Wallet, privateKey: PrivateKey): Wallet =
+  let publicKey = privateKey.toPublicKey()
+  let address = Address.init(publicKey.toCanonicalAddress())
+  Wallet(privateKey: privateKey, publicKey: publicKey, address: address)
+
+proc new*(_: type Wallet, privateKey: PrivateKey, provider: Provider): Wallet =
+  let wallet = Wallet.new(privateKey)
+  wallet.provider = some provider
+  wallet
+
+proc new*(_: type Wallet, privateKey: string): ?!Wallet =
+  let keyResult = PrivateKey.fromHex(privateKey)
+  if keyResult.isErr:
+    return failure newException(WalletError, "invalid key: " & $keyResult.error)
+  success Wallet.new(keyResult.get())
+
+proc new*(_: type Wallet, privateKey: string, provider: Provider): ?!Wallet =
+  let wallet = ? Wallet.new(privateKey)
+  wallet.provider = some provider
+  success wallet
+
+proc connect*(wallet: Wallet, provider: Provider) =
+  wallet.provider = some provider
+
+proc createRandom*(_: type Wallet): Wallet =
+  result = Wallet()
+  result.privateKey = PrivateKey.random(getRng()[])
+  result.publicKey = result.privateKey.toPublicKey()
+  result.address = Address.init(result.publicKey.toCanonicalAddress())
+
+proc createRandom*(_: type Wallet, provider: Provider): Wallet =
+  result = Wallet()
+  result.privateKey = PrivateKey.random(getRng()[])
+  result.publicKey = result.privateKey.toPublicKey()
+  result.address = Address.init(result.publicKey.toCanonicalAddress())
+  result.provider = some provider
+
+method provider*(wallet: Wallet): Provider {.gcsafe, raises: [SignerError].} =
+  without provider =? wallet.provider:
+    raiseWalletError "Wallet has no provider"
+  provider
+
+method getAddress*(
+  wallet: Wallet): Future[Address]
+  {.async: (raises:[ProviderError, SignerError]).} =
+
+  return wallet.address
+
+proc signTransaction*(wallet: Wallet,
+                      transaction: Transaction): Future[seq[byte]] {.async: (raises:[WalletError]).} =
+  if sender =? transaction.sender and sender != wallet.address:
+    raiseWalletError "from address mismatch"
+
+  return wallet.privateKey.sign(transaction)
+
+method sendTransaction*(
+  wallet: Wallet,
+  transaction: Transaction): Future[TransactionResponse]
+  {.async: (raises:[SignerError]).} =
+
+  convertError:
+    let signed = await signTransaction(wallet, transaction)
+    if nonce =? transaction.nonce:
+      wallet.updateNonce(nonce)
+    return await provider(wallet).sendTransaction(signed)

ethers/signers/wallet/error.nim

@@ -0,0 +1,13 @@
+import ../../signer
+
+type
+  WalletError* = object of SignerError
+
+func raiseWalletError*(message: string) {.raises: [WalletError].}=
+  raise newException(WalletError, message)
+
+template convertError*(body) =
+  try:
+    body
+  except CatchableError as error:
+    raiseWalletError(error.msg)

ethers/signers/wallet/signing.nim

@@ -2,9 +2,9 @@ import pkg/eth/keys
 import pkg/eth/rlp
 import pkg/eth/common/transaction as eth
 import pkg/eth/common/eth_hash
-import ../basics
+import ../../basics
-import ../transaction as ethers
+import ../../transaction as ethers
-import ../provider
+import ../../provider
 import ./error
 
 type

ethers/testing.nim

@@ -27,7 +27,7 @@ proc reverts*[T](call: Future[T]): Future[bool] {.async.} =
     else:
       discard await call
     return false
-  except ProviderError, EstimateGasError:
+  except ProviderError, SignerError, EstimateGasError:
     return true
 
 proc reverts*[T](call: Future[T], reason: string): Future[bool] {.async.} =
@@ -37,7 +37,7 @@ proc reverts*[T](call: Future[T], reason: string): Future[bool] {.async.} =
     else:
       discard await call
     return false
-  except ProviderError, EstimateGasError:
+  except ProviderError, SignerError, EstimateGasError:
     let e = getCurrentException()
     var passed = reason == (ref EthersError)(e).revertReason
     if not passed and

ethers/transaction.nim

@@ -1,3 +1,4 @@
+import pkg/serde
 import pkg/stew/byteutils
 import ./basics
 
@@ -6,8 +7,8 @@ type
     Legacy = 0,
     AccessList = 1,
     Dynamic = 2
-  Transaction* = object
+  Transaction* {.serialize.} = object
-    sender*: ?Address
+    sender* {.serialize("from").}: ?Address
     to*: Address
     data*: seq[byte]
     value*: UInt256
@@ -17,7 +18,7 @@ type
     maxFee*: ?UInt256
     maxPriorityFee*: ?UInt256
     gasLimit*: ?UInt256
-    transactionType*: ?TransactionType
+    transactionType* {.serialize("type").}: ?TransactionType
 
 func `$`*(transaction: Transaction): string =
   result = "("

ethers/wallet.nim

@@ -1,76 +1,3 @@
-import eth/keys
+import ./signers/wallet
-import ./basics
-import ./provider
-import ./transaction
-import ./signer
-import ./wallet/error
-import ./wallet/signing
 
-export keys
+export wallet
-export WalletError
-export signing
-
-var rng {.threadvar.}: ref HmacDrbgContext
-
-proc getRng: ref HmacDrbgContext =
-  if rng.isNil:
-    rng = newRng()
-  rng
-
-type Wallet* = ref object of Signer
-  privateKey*: PrivateKey
-  publicKey*: PublicKey
-  address*: Address
-  provider*: ?Provider
-
-proc new*(_: type Wallet, privateKey: PrivateKey): Wallet =
-  let publicKey = privateKey.toPublicKey()
-  let address = Address.init(publicKey.toCanonicalAddress())
-  Wallet(privateKey: privateKey, publicKey: publicKey, address: address)
-proc new*(_: type Wallet, privateKey: PrivateKey, provider: Provider): Wallet =
-  let wallet = Wallet.new(privateKey)
-  wallet.provider = some provider
-  wallet
-proc new*(_: type Wallet, privateKey: string): ?!Wallet =
-  let keyResult = PrivateKey.fromHex(privateKey)
-  if keyResult.isErr:
-    return failure newException(WalletError, "invalid key: " & $keyResult.error)
-  success Wallet.new(keyResult.get())
-proc new*(_: type Wallet, privateKey: string, provider: Provider): ?!Wallet =
-  let wallet = ? Wallet.new(privateKey)
-  wallet.provider = some provider
-  success wallet
-proc connect*(wallet: Wallet, provider: Provider) =
-  wallet.provider = some provider
-proc createRandom*(_: type Wallet): Wallet =
-  result = Wallet()
-  result.privateKey = PrivateKey.random(getRng()[])
-  result.publicKey = result.privateKey.toPublicKey()
-  result.address = Address.init(result.publicKey.toCanonicalAddress())
-proc createRandom*(_: type Wallet, provider: Provider): Wallet =
-  result = Wallet()
-  result.privateKey = PrivateKey.random(getRng()[])
-  result.publicKey = result.privateKey.toPublicKey()
-  result.address = Address.init(result.publicKey.toCanonicalAddress())
-  result.provider = some provider
-
-method provider*(wallet: Wallet): Provider =
-  without provider =? wallet.provider:
-    raiseWalletError "Wallet has no provider"
-  provider
-
-method getAddress(wallet: Wallet): Future[Address] {.async.} =
-  return wallet.address
-
-proc signTransaction*(wallet: Wallet,
-                      transaction: Transaction): Future[seq[byte]] {.async.} =
-  if sender =? transaction.sender and sender != wallet.address:
-    raiseWalletError "from address mismatch"
-
-  return wallet.privateKey.sign(transaction)
-
-method sendTransaction*(wallet: Wallet, transaction: Transaction): Future[TransactionResponse] {.async.} =
-  let signed = await signTransaction(wallet, transaction)
-  if nonce =? transaction.nonce:
-    wallet.updateNonce(nonce)
-  return await provider(wallet).sendTransaction(signed)

ethers/wallet/error.nim

@@ -1,7 +0,0 @@
-import ../basics
-
-type
-  WalletError* = object of EthersError
-
-func raiseWalletError*(message: string) =
-  raise newException(WalletError, message)

testmodule/mocks.nim

@@ -11,10 +11,15 @@ func new*(_: type MockSigner, provider: Provider): MockSigner =
 method provider*(signer: MockSigner): Provider =
   signer.provider
 
-method getAddress*(signer: MockSigner): Future[Address] {.async.} =
+method getAddress*(
+  signer: MockSigner): Future[Address]
+  {.async: (raises:[ProviderError, SignerError]).} =
+
   return signer.address
 
-method sendTransaction*(signer: MockSigner,
+method sendTransaction*(
-                        transaction: Transaction):
+  signer: MockSigner,
-                       Future[TransactionResponse] {.async.} =
+  transaction: Transaction): Future[TransactionResponse]
+  {.async: (raises:[SignerError]).} =
+
   signer.transactions.add(transaction)

testmodule/providers/jsonrpc/testConversions.nim

@@ -2,6 +2,9 @@ import std/strutils
 import std/unittest
 import pkg/ethers/provider
 import pkg/ethers/providers/jsonrpc/conversions
+import pkg/questionable
+import pkg/questionable/results
+import pkg/serde
 import pkg/stew/byteutils
 
 func flatten(s: string): string =
@@ -17,14 +20,14 @@ suite "JSON Conversions":
       "timestamp":"0x6285c293"
     }
 
-    var blk = Block.fromJson(json)
+    let blk1 = !Block.fromJson(json)
-    check blk.number.isNone
+    check blk1.number.isNone
 
     json["number"] = newJString("")
 
-    blk = Block.fromJson(json)
+    let blk2 = !Block.fromJson(json)
-    check blk.number.isSome
+    check blk2.number.isSome
-    check blk.number.get.isZero
+    check blk2.number.get.isZero
 
   test "missing block hash in Block isNone":
 
@@ -37,7 +40,8 @@ suite "JSON Conversions":
       }
     }
 
-    var blk = Block.fromJson(blkJson["result"])
+    without blk =? Block.fromJson(blkJson["result"]):
+      fail
     check blk.hash.isNone
 
   test "missing block number in TransactionReceipt isNone":
@@ -67,13 +71,15 @@ suite "JSON Conversions":
       "type": "0x0"
     }
 
-    var receipt = TransactionReceipt.fromJson(json)
+    without receipt1 =? TransactionReceipt.fromJson(json):
-    check receipt.blockNumber.isNone
+      fail
+    check receipt1.blockNumber.isNone
 
     json["blockNumber"] = newJString("")
-    receipt = TransactionReceipt.fromJson(json)
+    without receipt2 =? TransactionReceipt.fromJson(json):
-    check receipt.blockNumber.isSome
+      fail
-    check receipt.blockNumber.get.isZero
+    check receipt2.blockNumber.isSome
+    check receipt2.blockNumber.get.isZero
 
   test "missing block hash in TransactionReceipt isNone":
     let json = %*{
@@ -102,33 +108,10 @@ suite "JSON Conversions":
       "type": "0x0"
     }
 
-    let receipt = TransactionReceipt.fromJson(json)
+    without receipt =? TransactionReceipt.fromJson(json):
+      fail
     check receipt.blockHash.isNone
 
-  test "newHeads subcription raises exception when deserializing to Log":
-    let json = """{
-      "parentHash":"0xd68d4d0f29307df51e1284fc8a13595ae700ef0f1128830a69e6854381363d42",
-      "sha3Uncles":"0x1dcc4de8dec75d7aab85b567b6ccd41ad312451b948a7413f0a142fd40d49347",
-      "miner":"0x0000000000000000000000000000000000000000",
-      "stateRoot":"0x1f6f2d05de35bbfd50213be96ddf960d62b978b472c55d6ac223cd648cbbbbb0",
-      "transactionsRoot":"0xb9bb8a26abe091bb628ab2b6585c5af151aeb3984f4ba47a3c65d438283e069d",
-      "receiptsRoot":"0x33f229b7133e1ba3fb524b8af22d8184ca10b2da5bb170092a219c61ca023c1d",
-      "logsBloom":"0x00000000000000000000000000000000000000000020000000000002000000000000000000000000000000000000000000000000000008080000100200200000000000000000000000000008000000000000000000000000000000000000000000000800000000000000000000000000000000000000000000000010000040000000000100000000000800000000000000000000000000000000020000000000020000000000000000000000000000040000008000000000000000000020000000000002000000000000000000000000000000000000000000000000000001000010000000000000000020002000000020000000000000008002000000000000",
-      "difficulty":"0x2",
-      "number":"0x21d",
-      "gasLimit":"0x1c1b59a7",
-      "gasUsed":"0xda41b",
-      "timestamp":"0x6509410e",
-      "extraData":"0xd883010b05846765746888676f312e32302e32856c696e7578000000000000007102a27d75709b90ca9eb23cdaaccf4fc2d571d710f3bc5a7dc874f43af116a93ff832576a53c16f0d0aa1cd9e9a1dc0a60126c4d420f72b0866fc96ba6664f601",
-      "mixHash":"0x0000000000000000000000000000000000000000000000000000000000000000",
-      "nonce":"0x0000000000000000",
-      "baseFeePerGas":"0x7",
-      "withdrawalsRoot":null,
-      "hash":"0x64066c7150c660e5357c4b6b02d836c10353dfa8edb32c805fca9367fd29c6e7"
-    }"""
-    expect ValueError:
-      discard Log.fromJson(parseJson(json))
-
   test "correctly deserializes PastTransaction":
     let json = %*{
       "blockHash":"0x595bffbe897e025ea2df3213c4cc52c3f3d69bc04b49011d558f1b0e70038922",
@@ -149,7 +132,8 @@ suite "JSON Conversions":
       "s":"0x33aa50bc8bd719b6b17ad0bf52006bf8943999198f2bf731eb33c118091000f2"
     }
 
-    let tx = PastTransaction.fromJson(json)
+    without tx =? PastTransaction.fromJson(json):
+      fail
     check tx.blockHash == BlockHash(array[32, byte].fromHex("0x595bffbe897e025ea2df3213c4cc52c3f3d69bc04b49011d558f1b0e70038922"))
     check tx.blockNumber == 0x22e.u256
     check tx.sender == Address.init("0xe00b677c29ff8d8fe6068530e2bc36158c54dd34").get
@@ -198,12 +182,12 @@ suite "JSON Conversions":
         "nonce":"0x3",
         "to":"0x92f09aa59dccb892a9f5406ddd9c0b98f02ea57e",
         "transactionIndex":"0x3",
+        "type":"0x0",
+        "chainId":"0xc0de4",
         "value":"0x0",
         "v":"0x181bec",
         "r":"0x57ba18460934526333b80b0fea08737c363f3cd5fbec4a25a8a25e3e8acb362a",
-        "s":"0x33aa50bc8bd719b6b17ad0bf52006bf8943999198f2bf731eb33c118091000f2",
+        "s":"0x33aa50bc8bd719b6b17ad0bf52006bf8943999198f2bf731eb33c118091000f2"
-        "type":"0x0",
-        "chainId":"0xc0de4"
       }""".flatten
     check $(%tx) == expected
 
@@ -227,10 +211,12 @@ suite "JSON Conversions":
       "s":"0x33aa50bc8bd719b6b17ad0bf52006bf8943999198f2bf731eb33c118091000f2"
     }
 
-    let past = PastTransaction.fromJson(json)
+    without past =? PastTransaction.fromJson(json):
+      fail
     check %past.toTransaction == %*{
       "to": !Address.init("0x92f09aa59dccb892a9f5406ddd9c0b98f02ea57e"),
       "data": hexToSeqByte("0x6368a471d26ff5c7f835c1a8203235e88846ce1a196d6e79df0eaedd1b8ed3deec2ae5c00000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000006000000000000000000000000000000000000000000000000000000000000000012a00000000000000000000000000000000000000000000000000000000000000"),
+      "value": "0x0",
       "from": !Address.init("0xe00b677c29ff8d8fe6068530e2bc36158c54dd34"),
       "nonce": 0x3.u256,
       "chainId": 0xc0de4.u256,

testmodule/providers/jsonrpc/testJsonRpcProvider.nim

@@ -1,4 +1,3 @@
-import std/json
 import pkg/asynctest
 import pkg/chronos
 import pkg/ethers
@@ -97,5 +96,5 @@ for url in ["ws://localhost:8545", "http://localhost:8545"]:
         discard await provider.getBlock(BlockTag.latest)
       expect JsonRpcProviderError:
         discard await provider.subscribe(proc(_: Block) = discard)
-      expect JsonRpcProviderError:
+      expect JsonRpcSignerError:
         discard await provider.getSigner().sendTransaction(Transaction.example)

testmodule/providers/jsonrpc/testJsonRpcSubscriptions.nim

@@ -64,6 +64,7 @@ suite "Web socket subscriptions":
     client = newRpcWebSocketClient()
     await client.connect("ws://localhost:8545")
     subscriptions = JsonRpcSubscriptions.new(client)
+    subscriptions.start()
 
   teardown:
     await subscriptions.close()
@@ -81,6 +82,7 @@ suite "HTTP polling subscriptions":
     await client.connect("http://localhost:8545")
     subscriptions = JsonRpcSubscriptions.new(client,
                                              pollingInterval = 100.millis)
+    subscriptions.start()
 
   teardown:
     await subscriptions.close()

testmodule/testEnums.nim

@@ -1,5 +1,6 @@
 import pkg/asynctest
 import pkg/ethers
+import pkg/serde
 import ./hardhat
 
 type

testmodule/testReturns.nim

@@ -1,5 +1,6 @@
 import pkg/asynctest
 import pkg/ethers
+import pkg/serde
 import ./hardhat
 
 type

testmodule/testTesting.nim

@@ -3,6 +3,7 @@ import pkg/asynctest
 import pkg/chronos
 import pkg/ethers
 import pkg/ethers/testing
+import pkg/serde
 import ./helpers
 
 suite "Testing helpers":
@@ -31,12 +32,15 @@ suite "Testing helpers":
   test "reverts only checks ProviderErrors, EstimateGasErrors":
     proc callProviderError() {.async.} =
       raise newException(ProviderError, "test")
+    proc callSignerError() {.async.} =
+      raise newException(SignerError, "test")
     proc callEstimateGasError() {.async.} =
       raise newException(EstimateGasError, "test")
     proc callEthersError() {.async.} =
       raise newException(EthersError, "test")
 
     check await callProviderError().reverts()
+    check await callSignerError().reverts()
     check await callEstimateGasError().reverts()
     expect EthersError:
       check await callEthersError().reverts()
@@ -44,12 +48,15 @@ suite "Testing helpers":
   test "reverts with reason only checks ProviderErrors, EstimateGasErrors":
     proc callProviderError() {.async.} =
       raise newException(ProviderError, revertReason)
+    proc callSignerError() {.async.} =
+      raise newException(SignerError, revertReason)
     proc callEstimateGasError() {.async.} =
       raise newException(EstimateGasError, revertReason)
     proc callEthersError() {.async.} =
       raise newException(EthersError, revertReason)
 
     check await callProviderError().reverts(revertReason)
+    check await callSignerError().reverts(revertReason)
     check await callEstimateGasError().reverts(revertReason)
     expect EthersError:
       check await callEthersError().reverts(revertReason)

testmodule/testWallet.nim

@@ -1,4 +1,5 @@
 import pkg/asynctest
+import pkg/serde
 import pkg/stew/byteutils
 import ../ethers